Oil-well heater



A ril 28, 1925.

G. s HOLLISTER OIL WELL HEATER Filed July 13, 1922 2 Sheets-Sheet 2Patented Apr. 28, 1925.

UNITED STATES PATENT OFFICE.

GEORGE S. HOLLISTER, OF BURKBURNETT, TEXAS, ASSIGNOR TO JAMES B. PAULEY,TRUSTEE, OF CHICAGO, ILLINOIS.

OIL-WELL HEATER.

Application filed July 13,

To all whom it may concern:

Be it known that I, Gnouon S. HoLLIs'rnu, a citizen of the United Statesof America, and a resident of Burkburnett, county of lVichita, and Stateof Texas, have invented certain new and useful Improvements in OilellHeaters, of which the following is a specification.

My invention relates to apparatus for heating oil wells so as toincrease the flow of oil therefrom, and has for its object improvementsin such devices.

A typical oil well may be represented as a hole about six inches indiameter and extending down about two thousand feet, more or less. Atabout this depth is found a stratum of rock, as limestone, some live orten feet thick. Beneath this limestone is usually a stratum of sand fromwhich is obtained a flow of gas, and hence is called gas sand. Under thegas sand is found forty or fifty feet of oil sand resting on a rockfoundation. The hole is drilled down thru the oil sand and some eight orten feet into the rock foundation. That part of the. hole which is abovethe sandstone is lined with pipe or tubing, but that which is below isnot lined. The hole in the rock below the sand is in the nature of atrap or catch basin to receive sand caving in above.

Crude oil has a paraffin or an asphaltum base, and contains severalvolatile hydrocarbons. It is drawn from the well by a pumping operationwhich commonly places the oil sand under a comparatively high degree ofvacuum. Under these conditions the volatile oils change to gas, and inso doing they absorb heat and consequently cool the oil bearing sand orrock in the immediate neighborhood of the well. This cooling results insolidifying the parafiin or asphaltum in the pores in the sand thruwhich the oil must flow to be pumped. This process gradually seals thewalls of the well and stops the flow of oil. The remedy is to melt thesesolid deposits by the application of heat, and to pump them out whenmelted.

The best means for accomplishing this result is to use an electricheater, but there are a good many difliculties connected with, thisoperation and it is the object of the present construction to overcomethese difficulties. The hole to be heated is less than 1922. Serial No.574,649.

six inches in diameter, is frequently forty feet or more in length, andis down some two thousand feet below the surface of the earth. Theheater must be immersed in the oil in the well and that oil must serveas a circulating medium to convey heat from the heater to the walls ofthe well. An electric heater has a high temperature at the heatingelement, and such high temperature has a tendency to form carbondeposits from the oil. The device must be so constructed that suchdeposits will not short circuit the current flowing thru the heatingelement.

To heat the walls of a hole forty feet or more long, the heater which isimmersed in the oil of the well should be twenty feet or more in length.Such heaters are subject to two forms of peril, both of which have beenvery destructive to the heaters heretofore used. One of these is thatthe oil level in the well will sometimes subside and leave the upper endof the heater surrounded by gas in a confined space. Under suchcircumstances the ordinary heaters burn out at the upper end becausethere is no circulation of oil to carry away the heat generated in theheating element. Another menace which frequently destroys the heatersheretofore made is the caving in of the walls of the hole and theburying of the lower part of the heater in sand. Insuch cases the lowerpart becomes burned out and de stroyed. The present heater is designedto overcome the dangers arising from both of these conditions, neitherone of which can be avoided.

In the accompanying drawings I Fig. 1 is a section of the lower part ofan oil well, the present device being shown in elevation;

Fig. 2 is an enlarged elevation of the upper part of the device, theshell of which is shown in section;

Fig. 3 is a still more enlarged section of part of the devices shown inFig. 2;

Fig. 4 is a section on the same scale as Fig. 3 of the lower part of thedevice shown in Fig. 1; and

Figs. 5, 6. 7 and 8 are sections on correspondingly marked lines ofFigs. 3 and l.

The well is provided with a casing ll which extends down to thelimestone stratum which overlies the gas and oil bearing sand. Theheater is enclosed in a shell formed of parts 12 and 13 which areconnected to- 1 thru this pipe, and on the upperend of the pipeis astnihng. box 4C9 designed to prevent any quantity of water getting intothesectionlQ ot' the shell. l

The upper end of the coupling 14 is re duced in' diameter, andtheentire' coupling" is boredoutior the-reception of pipe 19; on thelower end of which is a cap 20. The

' upper end of coupling 14:- is counterbored to receive" the gland 21'of' a stulhng: box for V pipe 19, which pipe is screwed into said gland.The gland 2'1is held down'hy acap 22 which-is screwed on the outside ofthe upper end of coupling I l. Screwed upon the cap 22 is a short pieceof pipe 23, and on the upper end of this pipe is a block" which is boredout to form a second stuthng: box having a gland 25 and cap26.

Ata point near'the neck 16, the wire rope. 15' isbound' by wire' 27wrapped around it, and the wires of the rope are unwound to form strands28 which extend downward and thin holes 29in lugs 30 on coupling 14'.Thecore 3'1ofthe rope which is left when thesejstrands are unwoundcari'ies the insulated wires 3.2 and 33 and is the body which is packedagainst moisture by the upper stalling box 2 l-26. i

Theca'p 22 has its upper end closed by a plate 34'. thru which plate aresmall holes for the passage of insulated wires 35, andilb, which extenddown to heating elements helow; Above plate 34 these wires are spreadapart and have secured thereon" metallic connections 37 and 38 whichserveto form separable connections to the wires 32 and 38. The spacewithin the tube23ianld around the connections 37' and 38' is filled.with sheets of nica 51 which are bored out to receive said connections.

The wire 36 is connected thrir bridge 3 with the terminals 38 of heatingunitsSS), and wire is connected thru bridge 40 with terminals ll of twoother lieatiiigniiits of the same hind. Art the lower endsthese heatingunits are connected together by bridges and 43, the correspondingterminals of t'he'hea-ting units being indicated by 38 and' ll Theseheating units niay be 7 of any desired type, but those'illustrated inthe drawings are of the kind described in patent to Abbott, No.1,367,31, issued February 1,1921.

The heating units 39 are each inclosed in a inetaltube 44:, and the endsof these tubcs are secured firmly in blocked-5 and 46 as show-11in Fig.4. Secured upon the block 45 in liquid tight manner is the cap 20, and

similarly. secured to the block 46 is acap 4?. As constructed, theheating units and the caps protecting their electrical terminals aresuspended by pipe 19 from the gland 21 in the coupling 14, and thiscoupling in turn is suspended by strands 28 of rope 15. The shell 18 iscarried on the coupling l l and has its lower end closed by a plug 48.

@wing to the great length ofthe device as compared to its diameter, thedrawingsshow the parts broken oil. For the-purposes of abetterunderstanding it is desirable to give some of the diinen'sions founduseful, tho it should be understood that thesedi'niensions may be variedas circumstances may require. The shell will ordinarily be iron'r fourand one half' to live inches in di-' aineter. The distance betweenblocks 45 and 4-6 may conveniently be from twelve to six teen feet, andthe distance-from the cap 20 to the coupling ld may be some four or fivefeet. The coupling 14 and the plug d8 in'alze liquid tight jointsat' thetwoends of the shellisect'ion 13.

Assumingdiniensions such as those given, the" shell 13 is filled up tosome point between cap 20 and coupling 14 with some liquid, as herosene,which is a non-conductor of electricity. The space above the liquid isan air space, which it is desirable should be two' or three feet inlength. VViththe device in this condition it is lowered into-the wellto' a point about inid w-ay' of the) oil,

bearing sand or rock, and should be entirely immersed in the oil-in thewell; If the electric current be t'henturned on, the center or axialpart of the long column of kerosene will beheated by the heating units,and the outside of this column will be cooledby con tact of'the shell13'with the oil in the well; Under these conditionstherewill be set up aa circulation of the kerosene, which circulation' will consist; of acentral upward flow along the heating units and; an annular downwardflow along the inner wall of shell- 13 Thiswill convey heat from theheating units to the shell convection as distinguished from radiation",and from here it will be adiated thrtrthe wall of shell- 13 to the oilin the well. Fronr this point the heat will be conveyed partly byradiation, and partly by convection, to the sand or rock which: has itspores choked with congealed paraffin. I

If we assume that while this heating process is on, the walls of: theWell cave in and bury some four or five feet ofthe lower end of shell 13in a solid bed of sand, then all convection at this surface will ceaseand heat be conveyed to thev sand solely by radiation. As sand is acomparatively poor conductor of heat, this lower buried portion of thedevice will become overheated unless some means is provided to carryaway the heat and thus prevent such overheating. The circulatingkerosene is such means. The same is true in case the oil in the wellshould subside and leave the upper portion of the shell 13 surrounded bynothing but the gas in the well. The circulation of the kerosene willcarry the heat from the. overheated portions to the portions of shell 13which are in contact with oil in the well.

In oil wells there is always a certain amount of moisture, much of whichcondenses on the walls of the casing 11 and runs down into the well.Some of it also condenses on the rope15 and, it not prevented, will runinto the apparatus and short circuit the electric connections. Thestuffing box 49 is designed to prevent this, but it is not possible tomake a perfectly tight stufiing box for a wire rope. Some water will getby the stuffing box 4-9. The most of the water thus getting by thisstuffing box will run down the inside wall of the pipe 18 and the insidewall of shell sec tion 12 to the coupling 14. By an inspection of Figs.2 and 3 it will be seen that the space inside section 12 and abovecoupling forms a trap 50 into which water may accumulate until it. risesup to the top of cap 26 before it can find entrance to the electricalconnection. Of the water which runs down the rope 15, the greater partwill follow the strands 28 into the same trap. Of the water whichreaches the core 31 and follows down that core, a considerable quantitywill be deflected by the conical top to the cap 26 and will flow intothesame trap.

These various precautions are designed to prevent water from reachingthe electrical connection, but in spite of all precautions some waterwill get by in the long run. Such water will flow down the core 31 tothe mica sheets 51, and by capillarity will cause a short circuitbetween the terminals of wires 32 and at the place where they connectwith the connections 37 and 88. A short circuit at this point will causemuch less damage than would be caused by water running down the wires 35and 36 and causing a short circuit at the heating units.

The various devices involving the stuliing boxes and drainage into thetrap will ordinarily prevent water getting to the electrical heatingunits. The mica packing 51 and the electrical connections at 37 and 38constitute a safety device to protect the heating units in case theother devices should fail.

Heat is conveyed to the oil in the well, from the exterior of the shell13. The heating units are enclosed in metal tubes 4% which are immersedin a circulating medium contained within the shell 13. The quantity ofcirculating medium is sufficient to completely submerge all partsdirectly heated by the heating units. It will be noticed that thecirculating medium is not directly in contact with the heating units butis heatet indirectly thru the tubes i l, blocks 45 and lo, and caps 20and "71. It will also be noted that the oil in the well is not heateddirectly by the parts ust enumerated, but indirectly thru thecirculating medium and the shell 13. This process of indirect heatingeliminates the formation of carbon deposits which, in ordinary practice,have been found to occur and cause trouble at numer ous and unexpectedplaces and in numerous and unexpected ways.

lVhat I claim is:

1. In a device of the class described, a shell composed of two sectionsof tubular form, an interior coupling connecting the sections and havingan opening therethru, a pipe supported by the upper end of the couplingand extending downward thru the opening therein, a heating devicelocated in the lower section of said shell and supported by said pipe,and electrical connections extending downward thru said pipe to saidheating device.

2. In a deviceof the class described, a shell composed of two sections,a coupling connecting said sections, a heating device located in thelower section and supported by said coupling, electrical connectionsextending from the upper section thru an opening in said coupling to theheating device, a circulating fluid partly filling the lower section andsubmerging the heating device and means for protecting the electricalconnections from contact with the circulating fluid.

3. In a device of the class described, a shell composed of two sections,a coupling connecting the sections, a wire rope extending into the uppersection, said rope having its exterior wires separated from the corethereof and attached to the coupling for supporting the device, aheating device located in the lower section and suspended from thecoupling, and electrical connections extending from the core of the ropethru said coupling to said heating device.

4. In an oil well heater, a shell composed of two sections, a couplingconnecting the sections, devices mounted upon the coupling and extendingupward in the upper section, said devices being of less diameter thanthe interior of the shell so as to leave an annular space between theshell and the devices. a wire rope extending into the upper section ofthe shell and serving to support the apparatus, and electricalconnections extending from the core of the rope thru said devices andsaid coupling to the lower section, said parts being so constructed thatmoisture conextending to the heating element, and a trap Iii) formed inthe upper part of the shell and an ranged to receive and retain waterflowing down the rope.

6. In a device-of the class described, a shell having an electricheating element in the lower portion thereof and a Water trap in theupper portion, and a wire rope by which. the shell is supported, thestrands of said rope being so arranged that water running; down saidrope will be conveyed by said strands to said trap.

7. In a device of the class described, a shell having a water trap inthe upper portion thereof, a wire rope by which the shell is supported,and a pipe extending upward from the shell and serving to protect saidrope, said parts being so arranged that upon moisture entering the pipeand flowing down the interior wall of the pipe and down the exterior ofthe rope will be conveyed from both places to said trap.

8. In a device of the class described. a

shell, an electric heating element therein, a

rope by which the device is suspended, an

ment in case water gets past the retarding.

devices.

9. In a device of the class described, thecombination with a heatingdevice, an electric circuit therefor, and means for normally preventingwater from gaining entrance to the channel leading to the heatingdevice, of a safety device located in such channel and serving toshortcircuit the heating device by any water which may getpast themeansfor normally preventing such entrance.

10. In a device of the class described, the

combination with a heating unit, an electric circuit therefor, and meansfor normally preventing water fromv gaining entrance to:

the channel leading to the heating unit, of electrlcal connections 1nsaid circuit and located in said channel, and a strata 0t H1- sulatins;material such as mica filling such channel around said connections.

GEORGE S; HOLLISTERW

